The invention relates to a method for reducing the energy consumption of a motor vehicle having at least one electric onboard power supply to which at least one electric consuming device is connected.
The number of electric consuming devices in motor vehicles has increased considerably. In order to reduce the CO2 discharge in the vehicle, hydraulically operating consuming devices are being replaced by electric consuming devices. Thus, for example, an electric steering system (EPS) may replace a hydraulic steering system of the motor vehicle. However, for short periods of time, such electric consuming devices may make high power demands on the onboard vehicle power supply. This also results in a high demand on the stability of the onboard power supply of the motor vehicle. A sufficiently high electric voltage or electric power has to be available, particularly in the case of high loads occurring for short periods of time.
It is an object of the invention to provide a method that permits the implementation of an efficient onboard power supply and, in addition, the reduction of the energy consumption of a motor vehicle.
According to an aspect of the invention, there is provided a method of operating the internal-combustion engine in a first operating condition with a first injection quantity and with a first ignition point in time. For example, the electric generator of the vehicle and the battery of the vehicle jointly supply the onboard power supply in order to supply the electric consuming devices with a sufficient electric voltage. In the first operating condition, the generator may be running to capacity.
In a second operating condition, the internal-combustion engine is operated by a second injection quantity which is higher than the first injection quantity and with a second ignition point in time. With respect to the capacity of the internal-combustion engine, the second ignition point in time is less favorable in comparison to the first ignition point in time in the case of the second injection quantity. The second injection quantity, which is higher in comparison to the first injection quantity, increases the capacity of the internal-combustion engine per se and makes it possible for the internal-combustion engine to supply a torque that is higher per se to the electric generator of the motor vehicle. In a manner surprising to the driver, the rotational speed of the internal-combustion engine will increase without any countermeasure, so that the driver would have the impression that there is a defect. In order to compensate this torque increase, according to exemplary embodiments of the invention, the ignition point in time is adjusted from the first ignition point in time to the second ignition point in time in the second operating condition, whereby the capacity of the internal-combustion engine or its torque may be essentially reduced to the extent to which its torque has been increased by the increase of the injection quantity. The result of the second operating condition is a torque derivation of the internal-combustion engine, and the rotational speed of the engine remains largely constant during the transition from the first operating condition into the second operating condition.
In a third operating condition, the internal-combustion engine is operated with the second injection quantity and largely the first ignition point in time, so that the capacity or torque of the internal-combustion engine will be higher in the third operating condition in comparison to the second operating condition.
A driving situation detection device provided in the vehicle will detect a substantially imminent special driving situation on the basis of the driver's previous behavior when steering the vehicle or of the previous action of the vehicle beforehand and initiate that the internal-combustion engine changes from the first operating condition into the second operating condition. With the recognition of a substantially imminent special driving situation, a torque derivation of the internal-combustion engine is therefore caused according to exemplary embodiments of the invention by an increase of the injection quantity, which has the purpose of stabilizing the onboard power supply voltage if the latter will be necessary in the near future.
In an exemplary embodiment of the invention, the electric consuming device is an electrically actuated steering system, a chassis control system, or a chassis supporting system of the motor vehicle, and the substantially imminent special driving situation is a parking and/or maneuvering operation. This is a driving situation in which a low electric voltage in the onboard power supply becomes noticeable to the driver in a particularly unpleasant manner.
In the case of related art onboard power supplies, a delay of the load upon the electric generator is initiated when an electric consuming device that exercises a fairly high load upon the onboard power supply is switched on, such as an electric steering system. The consuming device is first fed from the vehicle battery and subsequently increasingly by the generator. Typically, this operation—the so-called load response—will last several seconds. As a result of this delay, more extensive rotational speed fluctuations of the internal-combustion engine are avoided when consuming devices with a high current demand are switched on.
In an exemplary embodiment of the invention, a greater electric load upon the onboard power supply, particularly in the third operating condition of the internal-combustion engine, is transmitted to the electric generator of the vehicle largely without delay. Thus, particularly in the third operating condition, no so-called load response operation is carried out.
In an exemplary embodiment of the invention, when a special driving situation is detected, the driving situation detection device causes the internal-combustion engine to change from the second into the third operating condition. As a result of the torque derivation in the second operating condition, because of the adjustment of the ignition point in time that can be technically implemented very rapidly during the transition to the third operating condition, the torque derived from the internal-combustion engine can be made available within a very short time. The internal-combustion engine will not die and can supply the required torque to the electric generator. The electric generator can feed a higher electric power into the onboard power supply, and the electric voltage is stabilized or will not break down despite a suddenly occurring higher load in the onboard power supply. Alternatively, when a special driving situation is detected, the driving situation detection device may cause the internal-combustion engine to change directly from the first into the third operating condition, without first changing into the second operating condition.
In an exemplary embodiment of the invention, the driving situation detection device recognizes the occurrence of the special driving situation by the fact that the electric voltage of the onboard power supply is about to break down. A monitoring of the voltage and, as required, a torque-increasing adjustment of the advance angle can be technically implemented in a relatively simple and cost-effective manner.
In an exemplary embodiment of the invention, the driving situation detection device takes into account who the actual driver is, as well as how he has previously acted. In particular, the actual driver can be recognized by the vehicle key used by him. This increases the hit rate of the prediction that a parking and/or maneuvering operation is imminent. When the driving situation detection device recognizes, for example, that the concerned driver always exhibits a characteristic approach, this hit rate for detecting an imminent parking and/or maneuvering operation will be increased.
In an exemplary embodiment of the invention, the driving situation detection device detects whether the speed of the vehicle falls below a predetermined threshold value, whether the reverse gear is engaged, and whether the difference between the absolute value of the actual steering angle and the absolute value of the steering angle is greater at an earlier point in time than a predetermined threshold value. The internal-combustion engine may be changed from the first operating condition into the second operating condition, and it is assumed that a so-called “reverse-steering operation” has occurred which represents a first of three alternatives for initiating a parking and/or maneuvering operation.
In an exemplary embodiment of the invention, the driving situation detection device detects whether the speed of the vehicle falls below a predetermined threshold value, whether the speed of the vehicle falls below the threshold value for a predefined time period, and whether the difference between the absolute value of the actual steering angle and the absolute value of a predetermined steering angle threshold value is greater than a predetermined threshold value. The internal-combustion engine may be changed from the first operating condition into the second operating condition, and it is assumed that a so-called “turn-steering operation” has occurred which represents a second of three alternatives for initiating a parking and/or maneuvering operation.
In an exemplary embodiment of the invention, the driving situation detection device detects whether the reverse gear is engaged, whether the speed of the vehicle falls below a predetermined threshold value, whether the difference between the absolute value of the actual steering angle and the absolute value of the steering angle is greater at an earlier point in time than a predetermined threshold value, whether the speed of the vehicle falls below the predetermined threshold value for a predefined time period, and whether the steering angle is greater than a predetermined threshold value. The internal-combustion engine may be changed from the first operating condition into the second operating condition, and it is assumed that a so-called “stationary-steering operation” has occurred which represents the third of three alternatives for initiating a parking and/or maneuvering operation.
According to another aspect of the invention, there is provided an onboard power supply of a motor vehicle which has a program-controlled driving situation detection device that carries out a method described above. Furthermore, a program-controlled driving situation detection device is provided that implements the method described above or causes its implementation.
In the following, the method according to exemplary embodiments of the invention will be explained in detail by flow charts using the example of a parking and/or maneuvering operation. The same reference symbols illustrate identical or identically acting functions.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.